ITBG20120010A1 - DEVICE FOR SURGICAL TRAINING - Google Patents

Description

Description of an invention patent entitled: "Device for surgical training"

DESCRIPTION

The present invention relates to a surgical training device. In particular, it refers to a device for the surgical training of lithotripsy (operation of crushing within the urinary tract of kidney stones).

Percutaneous lithotripsy (PCNL) is currently the main option in the treatment of large kidney stones.

This surgical technique involves the creation of a double operating field: one from the urethra for retrograde maneuvers, and one from the side for antegrade ones. To obtain percutaneous antegrade access to the kidney (nephrostomy), an ultrasound support is used to guide the operator in inserting a needle that generates the access route to the calculation. Once safe access to the kidney is achieved, the nephroscope is inserted to obtain a direct view. At this point, destruction is carried out (using ultrasonic, pneumatic, electro-hydraulic or laser probes) and subsequent removal of the aggregate.

The major risks associated with the entire procedure are related to nephrostomy and range from bleeding of the parenchyma (resulting in the need to postpone the procedure) to damage to organs adjacent to the kidney.

Consequently, an adequate training period of the operator in the execution of the ultrasound-guided renal puncture is essential.

A strategy usually used for the training of clinical staff is to use phantoms that allow the sequences of the procedure to be reproduced in a similar way to reality (in terms, for example, of landmarks, guidance systems, haptic feedback, etc.).

Some phantoms used for this purpose are known, such as the document US 5,055,051 which describes a body that reproduces the anatomical shape of the kidney obtained within a matrix that reproduces the acoustic properties of the liver. The volume is connected to the outside through appropriate channels, through which it is filled with ultrasound gel and materials that reproduce kidney stones. The procedure is simulated through the appropriate channels and the fragmented calculus is removed.

The object of the present invention is to provide a device for surgical training, in particular for lithotripsy, which reflects as much as possible the physical characteristics of human tissues.

Another object is to provide a device which is simple to manufacture.

A further object is to provide a device which can be reused several times.

In accordance with the present invention, these objects and others are achieved by a device for surgical training comprising: a first layer of synthetic material having a sound propagation speed between 1500 and 1550 m / s, and acoustic impedance included between 1, 5 and 1, 7 10 <6> Kg / sm <2>; a second layer of material inside said first layer comprising a kidney.

Further features of the invention are described in the dependent claims.

The advantages of this solution compared to the solutions of the known art are different.

First of all, the device or phantom allows access to the kidney from different angles and entry points, accentuating the potential of the device in terms of approach, typical of surgical training procedures.

Secondly, the device is reusable for simulating multiple procedures (in the order of tens).

Thirdly, similar to what happens in the operating room, a previously performed procedure leaves only a minimal surface trace and an internal ultrasound trace.

Fourthly, the choice of materials allows a simple realization of the puppet.

Fifthly, the puppet can accommodate different cartridges in successive times. For this reason the cartridges containing the kidneys are produced in special separate molds. The reuse of cartridges is in fact lower than that of the puppet. Moreover, in this way it is possible to carry out the training in succession on different pathological models. It is possible to devise a system for storing renal cartridges that involves the use of kidneys fixed in formalin, or fresh kidneys preserved with a cold chain or again with appropriate preservative agents and subsequent canning of the cartridge.

The characteristics and advantages of the present invention will become evident from the following detailed description of a practical embodiment thereof, illustrated by way of non-limiting example in the accompanying drawings, in which:

Figure 1 shows in section a device for surgical training according to a first embodiment of the present invention;

Figure 2 shows in section a device for surgical training according to a second embodiment of the present invention;

Figure 3 shows in section a device for surgical training according to a third embodiment of the present invention;

Figure 4 shows in section a device for surgical training according to a fourth embodiment of the present invention;

figure 5 shows in perspective and in partial perspective a mold for the realization of a device for the surgical training according to a third embodiment of the present invention;

Figure 6 shows in perspective a device for surgical training according to a third embodiment of the present invention.

The external and internal structures of the device or phantom 10 have morphological characteristics similar to the portion of the back involved in the procedure. The portion of interest for nephrostomy is that between the 11th <a> and the 12th <a> rib and the iliac crests.

Referring to the attached figures, a device or phantom 10 for the surgical training of lithotripsy, according to an embodiment of the present invention, is a substantially parallelepiped-shaped body which represents the portion of the bust defined previously and therefore two opposite sides of the parallelepiped correspond to two sections of the human torso.

The puppet 10 tries to simulate the organs present in this part of the body and surrounding the kidneys.

The tissues to be reproduced in the phantom can be reduced to a maximum of 5 (subcutaneous fat, muscle bands, liver, perirenal fat and kidney) in the hypothesis of not reproducing the viscera, not involved in the procedure of interest.

Alternatively, it is possible to foresee the reproduction of only 3 reproduced tissues, concentrated in the part of greatest interest: a single uniform layer representing the subcutaneous fat, the muscle and the liver, a layer for the perirenal fat and the kidney.

Seen in section, it has a substantially rectangle shape and comprises a first external material 11 that surrounds the whole device and represents the skin and subcutaneous fat, a second material 12, internal to the first, that surrounds the whole device and represents the muscle . It comprises, close to one side of the rectangle and centrally thereto, a third material 13, in a circular shape, which represents the vertebral column. The second material 12, in proximity to the third material 13, undergoes an enlargement and surrounds it. That is, the third material 13 (vertebral column) is completely surrounded by the second material 12 (muscle).

Lateral to the third material 13, symmetrically on both sides and slightly more in the center of the third material 13, there is a fourth 14 and a fifth 15 material, circular in shape, which represent the two kidneys. The fourth 14 and the fifth 15 material are surrounded by a sixth 16 and a seventh 17 material, respectively, in the shape of a circular crown representing the perirenal fat.

Throughout the internal part of the second material 12 (muscle) there is an eighth material 18 which represents the liver and the other organs. This material 18 also envelops the sixth 16 and seventh 17 materials (perirenal fat) which surround the fourth 14 material and the fifth 15 material (kidneys).

A simplification can provide for the creation of a reduced portion of the phantom 10 of figure 1. In particular, it is possible to consider making a phantom 20, taking into consideration only the right part of the abdomen (Figure 2), where the presence of the liver in the immediate vicinity of the kidney increases the criticality of the operation and the consequent training needs

In this case there is a structure identical to that of Figure 1 but reduced to only the portion that includes the portion on the left of axis II of Figure 1.

The procedure is in most cases performed with the patient in the prone position. It is therefore possible to further reduce the portion to be reproduced in the posterior quarter of the area of interest as shown in Figure 3.

In this case there is a phantom 30 having a structure identical to that of figure 2 but reduced to only the portion that includes the portion below the axis III of figure 2.

In one embodiment of the phantom 30, as shown in Figure 3, it has a rectangular shape whose width is 200 mm, the height is 150 mm, the diameter of the third circular material 13 (vertebral column) is 40 mm , the diameter of the fourth circular material 14 (kidney) is 90 mm, the thickness of the layers 11 (skin) and 12 (muscle) is 15 mm.

Finally, the shape of the puppet can be simplified by abstracting the structure until it assumes an axial symmetry, possibly giving up some landmarks such as the vertebral column. This configuration, at the expense of less anatomical and echogenic adherence, has the advantage of allowing access from multiple directions (theoretically along an angle of 360 °).

In this case there is a phantom 40 having a concentric ring structure. Starting from the inside, there is an internal material 41 which represents the kidney; a material with a circular sector 42, which surrounds the material 41, which represents the perirenal fat; a circular sector material 43, which surrounds the material 42, which represents the liver; a material with a circular sector 44, which surrounds the material 43, which represents the muscle; and finally a material with a circular sector 45, which surrounds the material 44, which represents the subcutaneous fat.

The materials used for the phantom must reproduce the physical characteristics of the tissues involved in the procedure (such as subcutaneous fat, muscle, abdominal organs, bone structures), in order to have an adequate response to the phantom's echo. This specification allows the operator to identify realistic landmarks, conforming to the standard ones of the procedure, by means of echoes, and to guide the nephrostomy accordingly.

Table 1 shows some of the physical characteristics of the tissues that must be reproduced in the phantom, where r represents the density, c the sound propagation speed, Z the acoustic impedance and a the attenuation coefficient. The measurements were carried out in normal working conditions for the use of the phantom and therefore at room temperature, and for the measurement of the impedance Z the frequency of the signal is between those normally used by ultrasound scanners and for example between 2 and 6 MHz.

The material used for the reproduction of the specific biological tissue must adequately reproduce the characteristics reported.

In addition, the materials must be pierceable with the appropriate surgical instruments. There should therefore be no preferential or pre-arranged channels for the introduction of surgical instruments.

The choice of materials for the realization of the phantom takes place after an experimental characterization of the acoustic properties of a shortlist of candidates considered suitable in terms of availability and workability.

The experimental apparatus used for measuring the acoustic properties of materials refers to the pulse-echo mode which uses a single probe that acts as both an emitter and a receiver. The ultrasonic probe is excited by a pulse generator (transmitter / receiver). The pressure wave generated by the excitation of the piezoelectric element is attenuated by propagating through the various layers of material (walls of the specimen of known size, and material to be tested) and is partially reflected by the discontinuities encountered along the path; the reflected components return to the transducer and are detected with a certain delay compared to the instant of emission. The reflected signal (echo) hitting the probe generates a potential difference between its electrodes and is retransmitted to the pulser / receiver which, by means of an oscilloscope, displays the trend of the electrical signal detected by the probe.

Downstream of the results of the preliminary tests, a synthetic material such as polyvinyl alcohol (PVA) was used.

In particular, polyvinyl alcohol (PVA) solutions were used, for example the one called Celvol® 165 from the company Sekisui Chemical CO, and distilled water, with concentrations from 5% to 12% by weight depending on the fabric to be reproduced, to model subcutaneous fat, muscle and liver; food gelatin for perirenal fat.

It has been found that it is preferable to use a concentration of distilled water in the measure of 5% for the subcutaneous fat, 12% for the muscle, 8% for the liver.

Inside the phantom it is planned to insert a biological sample of a porcine kidney, fresh or fixed in formalin, in turn incorporated into a structure (cartridge) of food gelatin. The cartridge can be removed from the phantom at the end of the training procedures and replaced with a new cartridge. Different models of cartridges can be envisaged that reproduce different pathological conditions (such as various morphologies and consistencies of stones, etc.). It is also planned to fill the kidney with urine simulating liquid in order to make the training procedure more realistic.

All the materials used for the realization of the phantom will be compact (including the joints between the different materials) and do not have pre-prepared holes.

For the realization of the phantom a mold 50 was created made with polymethylmethacrylate (PMMA). In the description reference will be made to a phantom 30 as shown in Figure 3.

The mold 50 comprises a base 51 (thickness 10 mm) two side walls (thickness 5 mm) 52 (longer) and 53 (shorter), of a thickness such as to give rigidity to the mold 50.

On the base and on the wall there are grooves in which removable bulkheads (thickness 1 mm) are placed to delimit the various parts.

An outermost bulkhead 55 joins the side walls 52 and 53.

An intermediate bulkhead 56, internal and equidistant from bulkhead 55, which also joins the side walls 52 and 53.

An internal bulkhead 57 which initially (starting from wall 52) slides equidistant from the previous bulkheads 55 and 56, and therefore has a recess (the distance between bulkheads 56 and 57 increases) before reaching wall 53.

Inside the bulkhead 57, near the curvature of the base 51 (and the relative bulkheads) there is a cylindrical spacer 58 which identifies the volume for the renal capsule. Yes also inserts a cylinder 59, preferably made of PMMA which simulates the spinal column, near the wall 53 which identifies the volume for the spinal column.

The volume between bulkhead 55 and 56 identifies the mold for subcutaneous fat, the volume between bulkhead 56 and 57 identifies the mold for muscle, and the volume inside bulkhead 57 identifies the mold for the liver.

The procedure for preparing the solutions involves mixing the PVA powder with distilled water in the indicated proportions. The mixture is then placed, in a closed container, in an oven at 90 °, for 6 hours and is allowed to cool to room temperature in order to obtain adequate boiling. The resulting compound is poured into the mold and subjected to at least one freezing cycle at -30 °, for 14 hours and thawed in order to obtain the desired physical properties.

A possible processing sequence can include:

- Insertion of the cylindrical 59 which identifies the vertebral column.

- Pouring of the mixture into the volume between the bulkheads 56 and 57 to obtain the muscle.

- Freezing cycle.

- Bulkhead removal 57.

- Insertion of the cylindrical spacer 58 which identifies the volume for the renal capsule.

- Pouring of the mixture into the volume inside the muscle for obtaining the liver.

- Freezing cycle.

- Bulkhead removal 56.

- Pouring of the mixture in the volume between the bulkhead 55 and the muscle to obtain the subcutaneous fat.

- Freezing cycle.

- Removal of bulkhead 55, walls 52 and 53 and base 51.

- Removal of the renal cartridge spacer.

- Inserting the renal cartridge.

The renal cartridge consists of a fresh or formalin-treated kidney, with or without simulated pathological conditions (stones), filled or not with liquid, immersed in a food gelatin matrix that simulates perirenal fat from the haptic and ultrasound point of view . In this case, the food gelatin was chosen because the values of the parameters correspond with those sought, for the ease of preparation and for its low cost. This part of the puppet, containing the kidney, which by its nature is perishable, so once used is eliminated and with it the gelatin layer, while the other part of the puppet can be reused several times and the material used is not perishable.

For the preparation of the gelatine sold in sheets: leave the sheets to soak for 10 minutes in water at room temperature, remove the excess water and melt them by heating them over a low flame. A quantity of water is added in relation to the concentration of gelatin to be obtained, for example of 40%. That is, 15 ml of water for every 6 g of gelatin.

The gelatin is poured into a mold having the shape of the cylindrical spacer 58, where a kidney is anchored in a suitable position. Cooling is carried out until the gelatin hardens. The cartridge is extracted from the mold and inserted into the volume of the cylindrical spacer 58, possibly with the aid of a layer of ultrasound gel to facilitate the elimination of air between the surfaces in contact.

The puppet is then ready for use.

In accordance with the present invention, the materials used best approach the values of human organs and in particular have characteristics as shown in Table 2, which reflect, with small variations, the values of Table 1. In particular, there are values of the propagation speed the sound c between 1500 and 1550 [m / s], the acoustic impedance Z between 1, 5 and 1, 7 [10 <6> Kg / sm <2>], and the attenuation coefficient a between 0 , 02 and 0.1 [dB / cm MHz]. The attenuation coefficient is the one that differs most from the optimal values but it is also the one that least affects the ultrasound response and is therefore considered secondary. On the other hand, the parameters that most influence the ultrasound response, that is the speed of sound propagation and the acoustic impedance Z, have values that are much closer to those desired.

The phantom, in accordance with the present invention, has significant improvements compared to those on the market, in fact it contains all the features necessary for the training of the entire surgical procedure in question. In particular, there is an adequate anthropomorphic representation of the back tract, a high representation of kidney stones, correct modeling of the internal structures interposed between the back and kidney, the possibility of using the ultrasound probe, the possibility of choosing the point in which to practice the nephrostomy (i.e. absence of predetermined accesses), the possibility of drilling the materials even with large-caliber instruments, the possibility of partial reuse of the structure.

The renal capsule is replaced almost at each intervention while the other structure can be reused several times and moreover, thanks to the material used, the openings that are made inside the phantom when the surgical instrument is withdrawn partially close and leave an echo. on the ultrasound, as for human patients.

TABLE 1

TABLE 2

Claims (8)

CLAIMS 1. Device for surgical training comprising: a first layer of synthetic material having a sound propagation speed between 1500 and 1550 m / s, and acoustic impedance between 1.5 and 1.7 10 <6> Kg / sm <2>; a second layer of material inside said first layer comprising a kidney. 2. Device according to claim 1 characterized in that said kidney is surrounded by said first layer. 3. Device according to claim 1 characterized in that said first synthetic layer comprises a third layer of external material; a fourth layer of intermediate material placed inside said third layer; a fifth layer of internal material placed inside said fourth layer. 4. Device according to claim 1 characterized in that said second layer comprises a kidney surrounded by a sixth layer of material having a sound propagation speed between 1500 and 1550 m / s, acoustic impedance between 1, 5 and between 1, 7 10 <6> Kg / sm <2>. 5. Device according to claim 4 characterized in that said sixth layer comprises food gelatin. 6. Device according to claim 3 characterized in that said first, third, fourth and fifth layers comprise a mixture made with polyvinyl alcohol and water with concentrations from 5% to 12% by weight. 7. Device according to claim 3 characterized in that said third layer comprises a mixture made with polyvinyl alcohol and water with a concentration of 5% by weight; said fourth layer comprises a mixture of made with polyvinyl alcohol and water with a concentration of 12% by weight; said fifth layer comprises a mixture of made with polyvinyl alcohol and water with a concentration of 8% by weight. 8. Device according to claim 3 characterized in that it comprises a seventh layer placed inside said fourth layer.